Keratoconus (ker-uh-toe-KOH-nus) occurs when your cornea — the clear, dome-shaped front surface of your eye — thins and gradually bulges outward into a cone shape.The cornea is the window of the eye. Light travels through the cornea past the lens to the retina and then the brain to form a visual image. The normal corneal surface is smooth and aspheric i.e. round in the center, flattening towards its outer edges. Light rays passing through it moves in an undistorted manner to the retina to project a clear image to the brain. A cone-shaped cornea causes blurred vision and may cause sensitivity to light and glare.
Keratoconus usually affects both eyes and generally occurs in people ages 10 to 25. In patients with keratoconus the cornea is not only cone shaped but the surface is also irregular resulting in a distorted image being projected onto the brain. The condition may progress slowly for 10 years or longer. Keratoconus typically commences at puberty and progresses to the mid-thirties at which time progression slows and often stops. Between age 12 and 35 it can arrest or progress at any time and there is no way to predict how fast it will progress or if it will progress at all. In general, young patients with advanced disease are more likely to progress to the point where they may ultimately require some form of surgical intervention.